Reaction times (RT), also called response times, and error rates (ER) on simple behavioral tasks have been shown to be valuable diagnostic tools for assessing the normality of cognitive or executive function of the human brain. Response time measures the amount of time it takes for a person to make a decision and effect a response following the presentation of a stimulus, and is a very common measure in experimental psychology to examine sensation, perception, cognitive, and motor function.
Cognitive dysfunction can arise with varying severity. Two commonly used clinical techniques are adequate to evaluate cognitive function in moderate to severe cases: brain imaging (functional magnetic resonance imaging, positron emission tomography, magnetoencephalography, or electroencephalography) and neuropsychological testing. Neuropsychological and imaging tests are generally not sensitive to detect subtle cognitive deficits. Neuroimaging methods are the least sensitive of all and are useful for predicting cognitive functional changes only if brain injury is moderate to severe. There are other problems beyond lack of sensitivity in neuropsychological and imaging techniques. The brain imaging technique is not portable, requires expertise to administer, and is slow to produce results. It is also very costly and is unsuitable for repeated use as would be needed for longitudinal monitoring. Neuropsychological testing also takes a relatively long time, requires expertise to administer and evaluate, and is very sensitive to language related issues. Some neuropsychological tests are unsuitable for repeated testing because of practice effects, learning, and strategies. These shortcomings negatively impact the ease of administration and interpretation and field applicability of these techniques.
Another clinical technique for measuring cognitive and executive functions in humans is eye movements. Eye movements have demonstrated brain areas important for processing visual stimuli and generating stimulus driven eye movement responses. Eye tracking devices track eye movements such as a saccade, which is a brain initiated quick simultaneous movement of both eyes in the same direction. Prosaccade eye movements involve a reflexive motor movement directly to a target. An antisaccade task is a voluntary eye movement task that involves inhibition of the reflexive movement towards the target and generation of a voluntary or goal directed movement of the eyes in the opposite direction of the target location20-22 (the superscripts refer to publications listed by numerical sequence in the “Publications” part of written description immediately preceding the Claims). An antisaccade test can be used to determine deficits in executive functioning.16-19 Several studies have demonstrated that eye tracking tasks are more sensitive than standard neuropsychological testing in detecting differences in cognitive or executive function12-14. For example, publication number 12 ((Hill S K, Reilly J L, Harris M S, Khine T, Sweeney J A (2008) Oculomotor and neuropsychological effects of antipsychotic treatment for schizophrenia. Schizophr Bull 34:494-506)) showed that eye tracking (or oculomotor) biomarkers were more sensitive to treatment-related changes in neurocognitive function than traditional neuropsychological measures.
Detecting mild cognitive dysfunction is extremely important because many of these mild problems if not detected early can lead to serious and sometimes fatal long-term outcomes. It is thought that less violent head impacts that are repeated in a short interval can be more damaging. This problem has reached national attention in the sport of professional football where subtle brain injuries have resulted in long term effects on memory and emotional functions and have raised awareness in a much greater population of people who participate in youth sports with potential for head impacts. Early detection of mild cognitive dysfunction is also very important for men and women in our armed forces as well as for emergency rooms throughout the country due to car or bicycle accidents and falls. Being able to track small changes in cognitive function will allow us to determine the most effective guidelines, interventions, and treatments. Cognitive deficits occur in many human brain disorders including psychiatric (e.g., schizophrenia), developmental {e.g., attention deficit hyperactivity disorder), and neurological {e.g., Huntington's disease). Detecting subtle differences in cognitive deficits is important for diagnosis or distinguishing subtypes that require different treatments or to identify the intervention, treatment or drug with optimal cognitive outcome. Thus early detection of mild cognitive dysfunction may also help with diagnosis, evaluation and discovery of treatments.
As mentioned, eye-tracking devices are able to detect subtle cognitive deficits with good temporal resolution for precise measurement of behavioral response times. Unfortunately, these devices are six figure expensive, time intensive, cumbersome, cause physical discomfort (wearing device(s) on the head, lengthy physical restraint of head requiring long motionless periods for accurate assessment), use elaborate and complicated machinery requiring complicated environmental control, require constant calibration and maintenance, necessitate training and expertise by someone with technical expertise to be accurate in administering the test, and require substantial data analysis.
There is therefore a great need for an inexpensive (thus potentially easily and widely available), portable and field operable, simple to operate device not needing constant calibration and maintenance for quick detection and monitoring of cognitive dysfunction, especially mild or subtle cognitive dysfunction, that can be used on school or professional sports sideline or locker room examinations, or in doctors offices or outpatient care, or in battlefield emergency care or other places in the field, or for low cost educational uses for health care professionals.
Recently, portable computing devices have become available that combine a display and a touch sensitive surface, allowing the user to interact with the display using touch with their own fingertips. However, in their current state, touch sensitive devices do not have touch temporal resolution sufficient to meet the need for in the field quick, accurate and precise detection and monitoring of cognitive dysfunction, especially mild or subtle cognitive dysfunction.